Washington Nationals first baseman Ryan Zimmerman, left, and second baseman Daniel Murphy (20) stand in the dugout in the sixth inning of a baseball game against the Cincinnati Reds, Monday, July 17, 2017, in Cincinnati. The Nationals won 6-1. (AP Photo/John Minchillo)

Washington Nationals' Brian Goodwin celebrates with Bryce Harper (34) after hitting a solo home run off Cincinnati Reds starting pitcher Asher Wojciechowski in the sixth inning of a baseball game, Monday, July 17, 2017, in Cincinnati. (AP Photo/John Minchillo)

Cincinnati Reds' Eugenio Suarez hits a solo home run off Washington Nationals starting pitcher Stephen Strasburg in the second inning of a baseball game, Monday, July 17, 2017, in Cincinnati. (AP Photo/John Minchillo)

Cincinnati Reds starting pitcher Scott Feldman (37) meets with manager Bryan Price, center, and catcher Tucker Barnhart in the first inning of a baseball game against the Washington Nationals, Monday, July 17, 2017, in Cincinnati. (AP Photo/John Minchillo)

Washington Nationals starting pitcher Stephen Strasburg throws in the first inning of a baseball game against the Cincinnati Reds, Monday, July 17, 2017, in Cincinnati. (AP Photo/John Minchillo)

Cincinnati Reds starting pitcher Scott Feldman (37) stands on the mound after giving up a solo home run to Washington Nationals' Ryan Zimmerman, right, in the first inning of a baseball game, Monday, July 17, 2017, in Cincinnati. (AP Photo/John Minchillo)

Washington Nationals' Ryan Zimmerman runs the bases after hitting a solo home run off Cincinnati Reds starting pitcher Scott Feldman in the first inning of a baseball game, Monday, July 17, 2017, in Cincinnati. Zimmerman's became the Nationals' career home run leader with 235. (AP Photo/John Minchillo)

CINCINNATI (AP) — The NL East leaders opened the second half of the season with a franchise record, a series sweep and a significant upgrade — exactly how the Nationals wanted to keep their momentum going.

Ryan Zimmerman set the Nationals' career home run record with a solo shot, and Bryce Harper connected again on Monday as Washington powered its way to a 6-1 victory for a four-game sweep of the Cincinnati Reds.

Zimmerman's 235th career homer moved him ahead of Vladimir Guerrero for most in Expos and Nationals history. Guerrero quickly tweeted congratulations , saying he doesn't mind being second.

"It's special to be in one place your entire career," said Zimmerman, in his 12th season with the team that made him a first-round draft pick. "You can't do stuff like this if you're not in the same place for a long time. So I feel very lucky to have spent my entire career here, honored to have hit more home runs than any Expo or National. It's cool."

The Nationals emerged from the All-Star break with an emphatically successful series — 13 homers, including three by Harper, and 35 runs overall by the league's top offense. It was the Nationals' first four-game sweep of the Reds and left them 6-1 against Cincinnati this season.

Washington improved to a season-high 20 games over .500 (56-36) with its ninth victory in 11 games.

The Nationals' roster got a little better during the series, too. Washington shored up its weak bullpen by getting relievers Ryan Madson and Sean Doolittle from Oakland on Sunday. They'll join the team in Los Angeles for the start of a series against the Angels on Tuesday.

"We know we have a good team and we've put ourselves in a good spot to start the second half, but we've got a ways to go," Zimmerman said. "Obviously we acquired two talented guys for the bullpen, and we'll just try to keep scoring runs so that they can come in and lock the games up."

Stephen Strasburg (10-3) recovered from his shortest start of the season by fanning 11 in seven innings and allowing four hits, including Eugenio Suarez's homer. Strasburg left his last start — a 13-0 loss to Atlanta on July 8 — after Nick Markakis' liner deflected off his hip in the third inning.

He allowed only two hits — including an infield single — in his last five innings.

"Your body wants to pretend it's the offseason," Strasburg said of the break between starts. "It took a little while to get going."

Scott Feldman (7-7) lasted only one inning, limited by a stiff right knee that has been bothering him. He gave up a double, a single, Harper's three-run homer and Zimmerman's solo shot in his first 12 pitches. Feldman left after facing nine batters and giving up five runs on 33 pitches.

"It wouldn't loosen up," Feldman said of the knee. "It was one of those days. I put the team in a tough spot. We were down five runs right off the bat."

Harper's homer extended his hitting streak to 12 games. Brian Goodwin's solo shot made it 6-1 in the sixth.

4 FOR 4

The last time the Nationals swept a four-game series was last season against Atlanta. It was the 11th four-game sweep in Nationals history.

KEEP RUNNING

Daniel Murphy scored from second base on Matt Wieter's fly out in the first inning, turning it into a sacrifice fly. Right fielder Scooter Gennett made a diving catch in the gap and then stumbled and dropped the ball while trying to get up, giving Murphy enough time to make it home.

STATS

It was Strasburg's sixth double-digit strikeout game of the season and the 35th of his career. ... Anthony Rendon extended his hitting streak to 11 games. ... Nationals starters allowed only one run in the series. ... The 13 homers allowed in a series matched the Reds' club record.

NATIONALS MOVES

Washington called up right-hander Jacob Turner from Triple-A. Right-hander Koda Glover — sidelined since April by a hip injury — was moved to the 60-day DL.

TRAINER'S ROOM

Nationals: CF Michael Taylor hasn't yet started baseball-related activities as he recovers from a strained right oblique. He went on the DL on July 7.

Reds: C Devin Mesoraco began a rehab assignment at Triple-A Louisville. He'll play a few games and be re-evaluated. He's been sidelined since July 5 with a strained left shoulder.

UP NEXT

Nationals: They face the Angels for the first time since 2011. Washington is 6-7 in interleague play this season.

Reds: RHP Sal Romano (1-1) will be called up to make his third career start when the Reds face the Diamondbacks. He also started on April 16 against Milwaukee and July 6 at Colorado.